Stainless steel of improved ductility

ABSTRACT

Stainless steel of improved ductility and cold rollability, more particularly, stainless steel which may be cold rolled from hot band directly to final gage without intermediate processing and annealing. In accordance with the invention, there is provided a stainless steel consisting essentially of up to 0.06% carbon, 0.2 to 1.0% manganese, 13 to 14% chromium, 0.2 to 1% silicon, 0.1 to 0.3% aluminum, 0.05 to 0.15% titanium and the balance essentially iron with usual steelmaking residuals.

United States Patent [191 Kalita Nov. 26, 1974 1 STAINLESS STEEL OFIMPROVED DUCTILITY [75] Inventor: Wesley Kalita, New Kensington, Pa.[73] Assignee: Allegheny Ludlum Industries Inc.,

Pittsburgh, Pa. [22] Filed: Apr. 12, 1973 [21] Appl. No.: 350,657

Related US. Application Data [60] Continuation of Ser. No, 162,474, July14, 1971, abandoned, which is a division of Ser. No, 860,036, Sept. 22,1969, abandoned.

[52] US. Cl. 148/12 EA [51] Int. Cl C21d 9/48, C22c 39/18 [58] Field ofSearch 148/12 EA [5 6] References Cited UNITED STATES PATENTS 2,736,6492/1956 Phillips 75/124 2,848,323 8/1958 Harris et a1. 75/124 3,250,6115/1966 Lula et a1 148/12 3,455,681 7/1969 Moskowitz et; al., 75/126 R3,607,246 9/1971 Kalita 75/126 D Primary Examiner-W. Stallard Attorney,Agent, or Firm\ incent G. Gioia; Robert F. Dropkin [57] ABSTRACT and thebalance essentially iron with usual steelmaking residuals.

6 Claims, N0 Drawings STAINLESS STEEL OF IMPROVED DUCTILITY Thisapplication is a continuation of now abandoned copending applicationSer. No. 162,474 filed July 14, 1971, which in turn is a division of nowabandoned copending application Ser. No. 860,036 filed Sept. 22, 1969.

Many stainless steels of improved corrosion resistance and physicalproperties which require relatively large amounts of alloying elementssuch as nickel or chromium are in existence, however, they arerelatively expensive and consequently, the usefulness of-such materialsis limited. There has been considerable effort to develop alloy steelswith adequate corrosion resistance having comparatively smaller amountsof expensive alloying elements. These compositions have served very wellin many applications. Frequently however, such compositions possesscomparatively poor ductility necessitating intermediate processing toproduce cold rolled material of usual sheet and strip thickness, thatis, less than about 0.02 inches. It has now been discovered thatstainless steel containing sufficient chromium to withstand standardsalt spray testing may be manufactured with sufficient ductility topermit direct cold reduction from hot band, e.g., 0.8 to 0.9 inchesthickness, to desired final gage without intermediate annealing.Compositions fulfilling this requirement in accordance with theinvention consist essentially of up to 0.06% carbon, 0.2 to 1.0%manganese, preferably 0.3 to 0.7% manganese, 0.2 to 1% silicon,preferably 0.2 to 0.5% silicon, 13 to 14% chromium, 0.05 to 0.15%titanium, 0.1 to 0.3% aluminum and the balance essentially iron withusual steelmaking residuals. Steels of the invention are useful in avariety of applications where moderate corrosion resistance is desired,such as trim on appliance, functional parts of cars, and indoorstructures.

To achieve the desired combination of properties including sufficientductility to be cold rolled direct to final gage from hot band, it isnecessary to critically control the compositional limits. The carbon ofthis alloy steel is limited to about 0.06% maximum since steels withgreater quantities of carbon may be somewhat difficult to weld due toformation of additional martensite. The upper limits of the alloyingelements, for example manganese and chromium, are restricted to avoiddeveloping unnecessary hardness and strength which would interfereunduly with formability. However, a chromium content of 13 to 14% ishighly desirable to assure the degree of corrosion resistance requiredfor a number of applications to which the present invention isparticularly well suited. Such compositions will successfully withstandstandard salt spray tests. The aluminum limits are established toprovide adequate weldability which is reduced if too little aluminum isincluded and to help assure adequate ductility and formability which maybe reduced if too much aluminum is present. Titanium is also included toimprove formability, but must be restricted to avoid developingundesirable metallurgical structures such as titanium stringers. Thepresence of titanium stringers also has an undesirable effect onstamping die Wear.

As an illustration of the practice of the invention,

coils of steel of the composition described in Table 1 were hot rolledto band gage. One coil (Heat 48805) was cold rolled to 0.077 inches withintermediate annealing and pickling, the other coil (Heat 32691 1)having a composition in accordance with the invention was cold rolleddirectly from hot band to 0.028 inches without intermediate annealing.The properties of these steels are shown in Table 11. As can be seen,the hardness steels of the invention are substantially less, indicatingsuperior ductility which permits direct reduction to final gage.

It is apparent from the foregoing that various changes and modificationsmay be made without departing from the invention, accordingly, the scopethereof should be limited only by the appended claims wherein what isclaimed is:

l. A method of manufacturing stainless steel strip, sheet or the likeless than 0.02 inches thickness which comprises hot rolling to band gagestainless steel consisting essentially of up to 0.06% carbon, 0.2 to1.0% manganese, 13 to 14% chromium, 0.2 to 1.0% silicon, 0.1 to0.3%aluminum, 0.05 to 0.15% titanium and the balance iron with usualsteelmaking residuals and thereafter cold rolling said hot rolled banddirect to a thickness less than 0.02 inches without intermediateannealing.

2. A method according to claim 1 wherein said steel contains 0.3 to 0.7%manganese.

3. A method according to claim 1 wherein said steel contains 0.2 to 0.5%silicon.

4. A method of manufacturing stainless steel strip, sheet or the likewhich comprises hot rolling to band gage stainless steel consistingessentially of up to 0.06% carbon, 0.2 to 1.0% manganese, 13 to 14%chromium, 0.2 to 1.0% silicon, 0.1 to 0.3% aluminum, 0.05 to 0.15%titanium and the balance iron with usual steelmaking residuals andthereafter cold rolling said hot rolled ,band direct to final gagewithout intermediate annealing.

5. A method according to claim 4 wherein said stee contains 0.3 to 0.7%manganese.

6. A method according to claim 4 wherein said steel contains 0.2 to 0.5%silicon.

1. A METHOD OF MANUFACTURING STAINLESS STEEL STRIP, SHEET OR THE LIKELESS THAN 0.02 INCHES THICKNESS WHICH COMPRISES HOT ROOLING TO BAND GAGESTAINLESS STEEEL CONSISTING ESSENTIALLY OF U TO 0.06% CARBON, 0.2 TO1.0% MANGANESE, 13 TO 14% CHROMIUM, 0.2 TO 1.0% SLICON, 0.1 TO 0.3%ALUMINUM, 0.05 TO 0.15% TITANIUM AND THE BALANCE IRON WITH USUALSTEELMAKING RESIDUALS AND THEREAFTER COLD ROOLING SAID HOT ROLLED BANDDIRECT TO A THICKNESS LESS THAN 0.02 INCHES WITHOUT INTERMEDIATEANNEALING.
 2. A method according to claim 1 wherein said steel contains0.3 to 0.7% manganese.
 3. A method according to claim 1 wherein saidsteel contains 0.2 to 0.5% silicon.
 4. A method of manufacturingstainless steel strip, sheet or the like which comprises hot rolling toband gage stainless steel consisting essentially of up to 0.06% carbon,0.2 to 1.0% manganese, 13 to 14% chromium, 0.2 to 1.0% silicon, 0.1 to0.3% aluminum, 0.05 to 0.15% titanium and the balance iron with usualsteelmaking residuals and thereafter cold rolling said hot rolled banddirect to final gage without intermediate annealing.
 5. A methodaccording to claim 4 wherein said steel contains 0.3 to 0.7% manganese.6. A method according to claim 4 wherein said steel contains 0.2 to 0.5%silicon.